Influence of seasonal drought on body condition and nutritional state in selected tropical birds

Nishikawa, Elise Toyoko

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https://hdl.handle.net/2142/105088 Copy

Description

Title

Influence of seasonal drought on body condition and nutritional state in selected tropical birds

Author(s)

Nishikawa, Elise Toyoko

Issue Date

2019-04-24

Director of Research (if dissertation) or Advisor (if thesis)

Brawn, Jeffrey D.

Department of Study

School of Integrative Biology

Discipline

Ecol, Evol, Conservation Biol

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Ornithology
• Neotropical
• Seasonal Drought
• Panama

Abstract

Tropical rainfall regimes have profound effects on the phenology and demography of resident organisms. Furthermore, evidence is emerging that the severity of seasonal drought can affect the viability of bird populations. For example, analyses on a long-term mark-recapture study in central Panama showed that longer dry seasons have a significant negative effect on population growth rates in nearly a third of the common bird species considered. Given the potential impacts on the resident biota, climate change projections predicting longer and more intense dry seasons are of particular concern. However, the ecological processes that underlie links between rainfall regimes and the population biology of tropical birds are unclear. Chapter 2 explores the influence of seasonal drought intensity on indicators of individual-level condition and nutrition across a suite of understory species. Changes in food-resource availability during seasonal drought is one possible mechanism driving the population level responses to dry season length in tropical birds. This project coincided with an extreme El Niño induced drought in central Panama, which allowed me to explore how seasonal drought intensity influences species and foraging guilds with differing sensitivity to dry conditions. I captured 258 birds from 27 species during the two focal dry seasons. I estimated individual condition using the scaled-mass index and I measured hematocrit in 371 collected blood samples, of which 319 were assayed for plasma lipid metabolites to examine nutritional state. The clearest evidence of elevated nutritional stress at the end of the extreme dry season came from a focal species for which longer dry seasons has a significant negative effect on population growth rates. Overall, I found mixed evidence for increased nutritional stress over the course of the dry season within focal species or among foraging guilds.

Graduation Semester

2019-05

Type of Resource

text

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http://hdl.handle.net/2142/105088

Copyright and License Information

Copyright 2019 Elise Nishikawa

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